1. Field of the Invention
The present invention relates to a light source drive control device, an image forming apparatus, a light source drive control method, and a computer program product.
2. Description of the Related Art
In recent years, digital printing machines using electrophotographic process are increasingly used in a production printing field. Therefore, higher image quality and higher reliability are demanded of the digital printing machine using the electrophotographic process. Particularly, improvement of reproducibility of thin lines, improvement of character reproducibility (improvement of reproducibility of characters of small size corresponding to, for example, two to three points), and suppression of character thickening owing to the electrophotographic process are demanded of the digital printing machine using the electrophotographic process.
For the purpose of achieving high image quality, the digital printing machine using the electrophotographic process includes an image processing unit that corrects image data by image processing. The image processing unit performs image processing with multiple-bit data at a high resolution of, for example, 1200 dots per inch (dpi) or 2400 dpi.
Examples of the digital printing machine using the electrophotographic process include, but are not limited to, a photoconductor drum whose surface functions as a photoconductive layer surface to be scanned, a light source that emits a laser beam, a polygon mirror that deflects the laser beam emitted from the light source, and a scanning optical system that guides the laser beam deflected by the polygon mirror to the surface of the photoconductor drum (surface to be scanned). The digital printing machine using the electrophotographic process modulates a beam emitted from the light source based on image data, irradiates the surface to be scanned with the beam emitted from the light source, and scans the surface to be scanned with the beam, thus forming an electrostatic latent image according to the image data on the photoconductor drum.
The digital printing machine using the electrophotographic process configured in the above manner uses an element, as the light source, having a plurality of light emitting points such as a laser diode array (LDA) or a vertical-cavity surface-emitting laser (VCSEL). Thus, the digital printing machine using the electrophotographic process can form an electrostatic latent image of, for example, 2400 dpi or 4800 dpi, which is higher resolution than that of image data of 1200 dpi.
Japanese Patent No. 4968902 and Japanese Patent No. 4640257 disclose an image processing method, implemented through processing in an image processing unit, for preventing collapse of a reversed character and improving character reproducibility by detecting a white part in an image to enlarge a white line or to correct pixels around a white letter.
Japanese Laid-open Patent Publication No. 2004-354986 discloses an exposure control technique upon image formation by an exposure optical device that forms an image using a plurality of exposure optical systems. An image forming method described in Japanese Laid-open Patent Publication No. 2004-354986 allows the reproducibility of small dots and thin lines to be improved, thereby improving the image quality.
However, the image processing method disclosed in Japanese Patent Nos. 4968902 and 4640257 has a problem that thin lines and characters of small size cannot clearly be reproduced.
Moreover, the image forming method disclosed in Japanese Laid-open Patent Publication No. 2004-354986 has a problem that thin lines and characters of small size cannot clearly be reproduced because the thin line formed in image forming process becomes thicker than an assumed line width with a decrease in the line width of the thin line of the image data.
In general, there is also a problem that the reproducibility of a thin line is decreased by performing correction to make a line width narrower by image data such that the thin line formed in the image forming process is not made thicker than the assumed line width, which leads to occurrence of defects such as blurring of thin lines.
In view of the above, there is a need to provide a light source drive control device, an image forming apparatus, a light source drive control method, and a computer program product capable of clearly reproducing thin lines and characters of small size.